Our proposed work continues our research concerning the interaction of behavioral and cardiovascular processes. The work takes two parallel paths. One phase of our work is concerned with the influence of sympathetic activity on the heart and vasculature during acute-intense behavioral stress. It involves an evaluation of stimulus conditions, individual differences and biological mechanisms that might evoke this effect. Of primary importance is the relevance of these sympathetic influences in the etiology of essential hypertension where studies are planned to evaluate sympathetic influences in humans with early or labile hypertension. It is also planned to develop in an animal model a hypertensive state so that more definitive work can be done with regard to hemodynamic events, the biological mediating mechanisms, and the relevance of behavioral stressors. A second phase is concerned primarily with tonic and phasic heart rate changes observed in simple, mildly stressful behavioral paradigms where we seek to determine the extent heart rate changes are associated with task relevant and irrelevant somatic effects. In turn, both cardiac and somatic effects are evaluated in regard to their sensitivity as indices of attentional processes and in regard to whether they can be used in the study of the etiology of attentional deficits in children with learning disabilities as well as diagnostic and prognostic tools.